1. Field of the Invention
The present invention relates to a heating device suitable for the process of manufacturing a semiconductor device, a method of manufacturing the heating device, and a processing apparatus using the heating device.
2. Description of the Related Art
In the process of manufacturing a semiconductor device, when surface processing for a semiconductor wafer on which devices are formed, for example, etching processing or CVD processing, is to be performed, a semiconductor wafer serving as an object to be processed is placed on a susceptor arranged in a processing vessel designed to have airtightness, and the processing vessel is evacuated to a predetermined low-pressure atmosphere. A predetermined process gas is supplied into the processing vessel. In this manner, predetermined processing is performed.
In this case, heating a semiconductor wafer to a predetermined temperature to perform predetermined processing has been conventionally used. A heating device for heating a semiconductor wafer is generally incorporated in the susceptor. A conventional heating device comprises a heating plate formed of a ceramic material such as Al.sub.2 O.sub.3 or AlN and a heating element formed of tungsten, and has a structure in which the heating element is simply inserted in a groove formed in a ceramic material in correspondence with the pattern of the heating element.
However, in the conventional heating device, Al.sub.2 O.sub.3 or AlN constituting the heating plate tends to form particles, so that contamination may occur in a processing vessel or on a semiconductor wafer. Since the inner surface of the processing vessel is exposed to various etching gas atmospheres, corrosion must be considered. However, the above ceramic material does not necessarily have a satisfactory resistance to corrosion. In addition, since the ceramic material has a low thermal shock resistance, the ceramic material cannot be abruptly increased or decreased in temperature, and must be used in a steady state. Since the heating device has the heating element simply inserted into the patterned groove, the heating element may be cluttered in the patterned groove, and particles may be formed by the cluttered heating element.
A degree of vacuum in the processing vessel is set to be high, for example, 1 Torr or less. At the high degree of vacuum, the dielectric breakdown level of a gas, i.e., a discharge start voltage level, is lowered, and discharge tends to occur. For this reason, there is no power supply method effective in the processing vessel, and a power supply path extending through the susceptor from the atmospheric side of the processing vessel must be formed. Therefore, this power supply path poses a problem on design for the heating device and maintenance.